Axial exchange currents and nucleon spin

We calculate the hypercharge and flavor singlet axial couplings related to the spin of the nucleon in a constituent quark model. In addition to the standard one-body axial currents, the model includes two-body axial exchange currents. The latter are necessary to satisfy the Partial Conservation of Axial Current (PCAC) condition. For both axial couplings we find significant corrections to the standard quark model prediction. Exchange currents reduce the valence quark contribution to the nucleon spin and afford an interpretation of the missing nucleon spin as orbital angular momentum carried by nonvalence quark degrees of freedom.Comment: 14 pages, 1 figur

Covariant Hamiltonian Dynamics with Negative Energy States

A relativistic quantum mechanics is studied for bound hadronic systems in the framework of the Point Form Relativistic Hamiltonian Dynamics. Negative energy states are introduced taking into account the restrictions imposed by a correct definition of the Poincar\'e group generators. We obtain nonpathological, manifestly covariant wave equations that dynamically contain the contributions of the negative energy states. Auxiliary negative energy states are also introduced, specially for studying the interactions of the hadronic systems with external probes.Comment: 42 pages, submitted to EPJ

Light Cone QCD Sum Rules Analysis of the Axial N -> Delta Transition Form Factors

The axial N-> Delta(1232) transition form factors are calculated within the light cone QCD sum rules method. A comparison of our results with predictions of lattice theory and quark model calculations is pre- sented.Comment: 31 Pages, 9 Figure

Partial conservation of the axial current and axial exchange currents in the nucleon

We discuss the axial form factors of the nucleon within the context of the nonrelativistic chiral quark model. Partial conservation of the axial current (PCAC) imposed at the quark operator level enforces an axial coupling for the constituent quarks which is smaller than unity. This leads to an axial coupling constant of the nucleon $g_A$ in good agreement with experiment. PCAC also requires the inclusion of axial exchange currents. Their effects on the axial form factors are analyzed. We find only small exchange current contributions to $g_A$, which is dominated by the one-body axial current. On the other hand, axial exchange currents give sizeable contributions to the axial radius of the nucleon $r_A^2$, and to the non-pole part of the induced pseudoscalar form factor $g_P$. For the latter, the confinement exchange current is the dominant term.Comment: The formal part of the paper developped in sections III and IV has been clearly improved. The numerical results change slightly. A few new references added. Version accepted for publication in Nuclear Physics

Early Appearance of Epicardial Adipose Tissue through Human Development

Background: Epicardial adipose tissue (EAT) is a visceral fat depot with unique anatomic, biomolecular and genetic features. Due to its proximity to the coronary arteries and myocardium, dysfunctional EAT may contribute to the development and progression of cardiovascular and metabolic-related adiposity-based chronic diseases. The aim of this work was to describe, by morphological techniques, the early origin of EAT. Methods: EAT adipogenesis was studied in 41 embryos from 32 gestational days (GD) to 8 gestational weeks (GW) and in 23 fetuses until full term (from 9 to 36 GW). Results: This process comprises five stages. Stage 1 appears as mesenchyme at 33–35 GD. Stage 2 is characterized by angiogenesis at 42–45 GD. Stage 3 covers up to 34 GW with the appearance of small fibers in the extracellular matrix. Stage 4 is visible around the coronary arteries, as multilocular adipocytes in primitive fat lobules, and Stage 5 is present with unilocular adipocytes in the definitive fat lobules. EAT precursor tissue appears as early as the end of the first gestational month in the atrioventricular grooves. Unilocular adipocytes appear at the eighth gestational month. Conclusions: Due to its early origin, plasticity and clinical implications, factors such as maternal health and nutrition might influence EAT early development in consequence

Evaluación de la satisfacción de los estudiantes de diferentes grados del área de Ciencias de la Salud, mediante la utilización de la plataforma Kahoot

El presente proyecto es una propuesta para evaluar la satisfacción de estudiantes universitarios sobre la planificación y el desarrollo de la actividad docente, en distintas asignaturas pertenecientes al Área de Ciencias de la Salud durante el curso 2017-2018, mediante el diseño de cuestionarios específicos y el uso de la plataforma Kahoot

Píldoras de aprendizaje: Vídeos de corta duración en la docencia del Grado de Medicina

Los mini-vídeos pueden ser considerados píldoras de aprendizaje (llamadas píldoras de conocimiento), ya que durante su visionado se accede rápidamente a una información concreta, cuya única finalidad es reforzar otros materiales didácticos, mejorar la comprensión de los contenidos de la asignatura y aumentar la motivación de los estudiantes. Dado los beneficios del uso de estos recursos didáctico, un grupo de profesores de la Facultad de Medicina, una investigadora del Área de Ciencias de la Salud y un Médico del Servicio de Medicina Intensiva del Hospital Clínico San Carlos diseñaron mini-vídeos para utilizarlos en la docencia de la asignatura de Bioquímica Humana de segundo curso del Grado de Medicina. La preparación de cada mini-vídeo ha supuesto un arduo trabajo tanto en la elaboración como en el diseño de los elementos que integran cada recurso audiovisual. Sin embargo, el resultado ha sido muy satisfactorio tanto para los estudiantes como para los docentes que participaron en esta experiencia

Theoretical uncertainties on quasielastic charged-current neutrino-nucleus cross sections

We estimate the theoretical uncertainties of the model developed in [J. Nieves, J.E. Amaro, M. Valverde, Phys. Rev. C 70 (2004) 055503] for inclusive quasielastic charged-current neutrino-nucleus reactions at intermediate energies. Besides we quantify the deviations of the predictions of this many body framework from those obtained within a simple Fermi gas model. A special attention has been paid to the ratio sigma(mu)/sigma(e) of interest for experiments on atmospheric neutrinos. We show that uncertainties affecting this ratio are likely smaller than 5%